This made me lol. I’ve been using an air purifier solely for the purpose of generating white noise. I don’t recall when I started doing this, but it’s been many, many years. The functionality of the air purifier wasn’t even a thought in my mind.
An air purifier is the best noise machine for me, much better than the white noise machines with the tinny speakers. Even the brown noise setting on those isn't nearly deep enough to let me sleep.
Totally agree. I've never liked the speaker generators. The old school DOHM models are way better because they do not use a speaker, they have a fan inside.
The bigger the fan the better, IMO. I really love those cheap square box fans... It's hard to beat that deep, low hum that small speakers and small fans just can't replicate.
Now that I think of it, back when I was a kid in the 90s, there was a circa-70s oscillating fan that my family kept in the living room during the summer, and the noise it made was quite pleasant. The oscillation added a gentle rhythmic quality that made it even nicer.
I’d never put two and two together until now, but that fan had to have been a major factor in some of the unexpectedly great naps in that room.
We had a circulating fan from the 50s that had very little in way of a cage with metal blades. The fan was heavy as you might imagine from the time period. It worked great. It was definitely something we were repeatedly warned about it as kids to not put fingers/hands in it. The house was a pier&beam with the AC vents in the floor. The fan sat on the floor next to one of the vents to blow towards the couch. I'd agree that it had influence on naps as well
There are 20" square box fans that have a built in slot for a 20x20x1 filter. It's advertised as having a slightly more powerful motor. It is a good noise machine while also getting the added benefit of filtered air instead of just noise
You can easily send white noise to good speakers, if you have any. There are free apps for it, not to mention hours-long YouTube videos with white/pink/brown noise.
Yea, having it and using it at max just as I go to bed just makes me feel much better for the air I'll be breathing while sleeping. I also used to always fall asleep to some noise or music, so this is such a nice replacement
None of those seem particularly concerning. We have a gas range, and 15 min past the end of cooking everything is fine. I must imagine that most people don't live right next to the freeway so they probably have even better air quality except during wildfire season.
CO2 - I'm thrilled with anything less than 800 ppm (half justified by being the lowest number I've ever seen a study suggest might have health effects, half justified by being at a point where I personally don't notice that I'm more drowsy).
PM2.5 - My impression is the health risks here are more cumulative exposure (and include things I'd like to go without in my life, like alzheimers) and a pretty straight line of "lower is better all the way to zero". The WHO's guideline is mean exposure of 5 µg/m³ so I guess I'd adopt that if I had to put a number on it. (But it's a mean, I wouldn't worry about briefly exceeding it)
PM10 - No real opinion (I'd rather worry about PM2.5)
VOC index - I'm not sure this is a standardized thing, but the version I've come across is an index relative to the average that particular sensor has seen in the last 24 hours. So there's no standard possible here.
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As for a gas range I would worry about NOX considering the studies with them causing and aggravating asthma. That said your CO2 levels are low so I suspect you might have sufficient ventilation that this isn't a huge issue for you (especially if that ventilation is in the form of a fume hood over your stove that you actually use).
CO2 by itself doesn't appear to be a problem until some truly absurd levels are somehow achieved.
CO2 is usually a proxy for air quality because outside is usually something consistent like 400 therefore deviation from that figure indicates staleness.
I don't have the list of relevant studies I've read on hand atm but there was at least one where they simply pumped in CO2 (or didn't) and had an effect showing pretty directly that CO2 itself is problematic at reasonably low levels - as well as potentially being an excellent proxy for other air quality issues. Problematic in a "makes you drowsy/stupid" type of way - not a "kills you" type of way. Though there's also at least one correlative studies suggesting it might have long term health effects (which really wouldn't be surprising if it has any short term effects).
Besides which, proxy or directly high CO2 means you should ventilate...
the military has conducted studies where submariners were exposed to a PPM of 1000s with no ill effect. I suppose they were trying to determine how hard they need to scrub.
having said that, it's possible they omitted what other gasses and %s they used for advantage. there could be some mitigation possible there.
VOC index means literally nothing. (I've read the datasheet, implemented some kludges to log raw data, and contemplated the formulas. The data is high-pass filtered. You literally cannot conclude anything about a single measurement if you assume the sensor is somehow magically perfect. You might conclude that there is more VOC (or less -- not all VOCs have the same sign in their effect) when cooking than when not cooking.)
I target 0 PM2.5, but this only necessarily makes sense as a target if you have the ability to filter your home's supply air. And a good vent hood should be able to avoid any detectable bump while cooking (although a vent hood without filtered makeup air may cause a bump due to increased infiltration of exterior air).
What sensor, exactly, are you describing here? Different VOC sensors have different gas sensibilities, as well as different algorithms to interpret the gas sensor raw data.
The instrument is pretty crappy - it has basically no calibration or, AIUI, long term stability. So you can’t really use it to characterize the chemical content of the air. What you can do is observe changes. I’m guessing the manufacturer wanted to avoid people getting confused by the absurd raw reasons, so they came up with a formula called “VOC Index” that HPFs the data. It will average 100 IIRC. You’re supposed to use it to notice events that cause changes - if it hits 170 every day at 2 PM them you can guess that something’s happening at 2 PM.
None of this is in the chip. It’s implemented by the driver. There’s an implementation in esphome, for example.
pm10 is the mass concentration of particles with aerodynamic diameters up to approximately 10 µm, including PM2.5, so Jefftk's analogy was right. there must some kind of typo or measurement error
Depending on the month, my kitchen AQI averages between 1-4, representing PM2.5 values of 0.1 - 0.8 ug/m^3. Bedrooms are likely better as they don't have the gas stove.
CO2 while occupied is generally under 750; I'd prefer to keep it under 700 but we also balance that with energy efficiency for that make-up air; I don't have an ERV, so we suffer a little there.
(We don't live by a freeway but - (a) Pittsburgh's air isn't great; and (b) the canadian wildfires were pretty bad here at times this summer, and that was what caused that 0.8 ug/m^3 pm2.5 spike).
We have, um, a lot of air filters left over from covid, though, so we're a little spoiled in terms of being able to manage AQI easily.
I have 4 Coway and 2 Winix purifiers and I can confirm: they're great sleep noise generators! The plastic front pieces and the filters themselves block/baffle any high frequency noise from the fans, leaving you with a pleasant low/mid frequency whooooooosh. I like it better than the sound from small cheap solid state machines; their small speakers can't do low frequencies.
For most circumstances where someone would use
a white noise machine, this kind of small purifier
is all-around better.
Hmm. The word "most" is doing a lot of work here.
Depends if you enjoy fresh air when you sleep or not. If you've ever monitored CO2 levels you know how quickly they climb in a closed room.
But, if you are blowing fresh air into a room, or have the windows open, the filtration effectiveness of these units approaches zero pretty rapidly. And these air purifiers aren't exactly free to run: they use ~50-100W of power and if you run them 24/7 you can expect to spend $100+ per year on filters.
>if you are blowing fresh air into a room, or have the windows open, the filtration effectiveness of these units approaches zero pretty rapidly
Even with an open window, if (say) the air purifier and the window have a flow of 200 CFM, then the air will still be twice as clean (ie half as many pollution particles). I would say that's still worth doing!
Most people would just leave the window open <1", which keep CO2 down yet air purifiers still work well.
That’s the design appeal of ionizers like BlueAir (not most ionizers, but specially those designed to supposedly prevent ozone production). They comparatively sip power while getting the same measured reduction in particulates and ozone.
I've been using the air purifier as a white noise machine for 5 years and I couldn't be happier. Currently sitting in a room with PM2.5 at 1 µg/m³
I bought the Ikea (FÖRNUFTIG) because I was worried that lesser known brands on Amazon might go out of business, making it hard to find replacement filters later
My partner and I were just discussing whether our air purifier actually does something other than make noise, and whether the air quality indoors is better or worse than outdoors.
I bought some levoit core 300s purifier and after a minute it seemed to have made air so dry i started to have dry throat and light coughing. Thought I'd need a humidifier too .. but I just sold it back.
Noise pollution is known to have adverse health effects, maybe its better to not cover one noise with another, even louder one? Or invest in sound insulation, damage compounds over decades.
Many people don't have the option to isolate their houses better.
But, if I'm not mistaken, the damage you speak of is caused by disrupting sleep. So the idea is that if a white noise generator can drown out the interruptions, it helps you sleep better. There are studies that say noise doesn't help, and there are those that say it does. And it's all real-life medical research, so pretty unreliable. I found one controlled study (https://doi.org/10.1093/sleep/zsag001), but it's small, and only 7 days, and it's in a lab, so not guaranteed to translate to normal conditions either.
And don't ignore the placebo effect. Perhaps believing that pink noise helps is sufficient for some.
Perhaps a better recommendation is good ear plugs.
I bought a large soldering iron air purifier and it turns out to be great; it has a continuious speed selector, easy to replace filters, and very pleasant spectrum. I like it better than the air conditioner, which cycles on and off noisily.
You can make your own to save money, I made this project for example. I paired it with an Air-1 sensor and home assistant to ramp up and down the downs in real time according to the live air quality readings.
Filters are included, as well as high quality fans, AC/DC converter and speed controller, and the portable/collapsible enclosure. It's really not that expensive vs trying to put together the parts yourself, and it's tested to work very well compared to other more expensive filters.
Those fans will not have sufficient static pressure to be useful. These makeshift purifiers may be great in a pinch (wildfire season and stores are all out), but far from the best.
This is indeed the "conventional wisdom," but if you do the math it turns out this is incorrect.
The trick is to use high-airflow MERV 13 filters (ideally 3M 1900, which has high pleat count and low resistance) instead of high-resistance HEPA filters, so axial PC fans can generate enough pressure.
You want at least MERV 15 so that virus sized particles get filtered in meaningful amounts, but yes the guy above you is wrong and choking on dirty air
Merv-13 means it filters at least 75% of the particles passing through it.
For a standalone air filter which is pushing the filtered air into the same room its drawing from, we can assume reasonably good mixing of the intake and exhaust air. Thus to be equivalent to a HEPA-filter it only needs 1/3rd more airflow... Which really isn't much.
This doesn't follow for a a fancier setup where you're taking dirty air and blowing it into a cleanroom or something... but that's not how we're typically using household air filters.
Is it safe to assume all particles are equally as likely to be filtered, or are there particles that HEPA will filter that a MERV-13 will never filter no matter the number of cycles?
75% refers to the Most Penetrating Particle Size (MPPS), so they intentionally measure at the worst-case size so you don't have that problem. All other sizes are filtered at a higher percent.
The linked PC-fan purifier has been tested and shown to purify air faster than the conventional alternatives, and are not makeshift, so I'm not sure what you are referring to.
From the specs it looks like they are probably closer to higher-static-pressure server fans, the CADR is a few hundred CFM and it pulls 30+ watts. And as with many of these designs, you can compensate for low pressure performance by increasing filter surface area... the greater the surface area the lower the pressure drop. Of course, the problem with this is you are just spending more money on filters, which is the expensive part.
The filter cost for the AirFanta 3 doesn't seem particularly high? In fact it seems cheaper than competitors.
All the purifier companies realized they make more money selling overpriced filters, so $60+ for the OEM filters is common nowadays. Despite it just being a standard HEPA filter cut to a specific size.
Airfanta 3 Pro filters (four) - $57
Coway Mighty Filter - $60
Coway Mighty2 Filter - $70-$80
I'd be concerned about the availability of filters after a few years. Some of these companies have been changing their models and filter type every year to add some nebulous feature. Others just go out of business.
Yeah, the retail prices of filters is all over the place because of the popularity of razor/blade model of pricing. I'm not talking about that, I'm talking about the BOM itself -- this device is using 4x the filter media of comparable filters, which would typically have one filter that size.
HEPA media itself is a commodity and aftermarket filters (and the BOM cost to the OEM) tend to level out at whatever rate is minimally profitable per area of filter media.
The upfront cost of this device is high for what you get, because you're mostly buying filter media. The device itself is not much of a polished product. I'm sure it works fine but I wouldn't want one in my living room.
But since you bought mostly media, you didn't get a housing that hides the media, and you get to look at any collected dirt for that longer interval as well...
I'm sure it works but like any engineering decision it has pros and cons.
If that's your biggest worry in life, seems like a high-class problem! Many people are satisfied 'just' protecting their heart and lung health.
However, if you really don't want to look at it, you can always flip most DIY designs inside-out so the fans blow in and dust collects on the inside instead of the outside! This doesn't clean the room quite as efficiently, but if the appearance of dust is a major concern that should be a fix.
Yeah it’s functionally fine but I would opt to buy a more polished product for the above reasons. Probably would be great for a shop or similar, which is where I’ve done DIY purifiers myself. My personal favorite for cutting down on dust during home projects is a 20x20 furnace filter slapped on the intake side of a box fan. It requires zero extra parts or assembly.
Flipping the fans isn’t great because then you have to clean the fans, this is why draw-through is the standard configuration. Also many designs like this rely on negative pressure to seal properly or even stay together. You might just have the lid take off like a helicopter.
The Austin Air HealthMate is great as a noise machine. Very loud. It’s a HEPA filter and lasts 5 years. Never seen any other that lasts that long, but you pay for it upfront. after-market replacements are $250-300 for another 5 years.
I have that machine. It seems better at filtering chemicals and VOCs but not great at filtering particulates. It gets rid of odors very well but my PM2.5 meter barely budges.
I have IQAir HyperHEPA filters, plus whole-house AprilAire HEPA filters on the HVAC equipment in the attic. I’m fine on particulates.
Where I need extra help is with VOCs in certain locations. Like, in or near bathrooms. Or the cat litter boxes. IQAir does sell their GC line for that, and we have a couple of those. But the activated carbon filter media is super expensive. And these things are huge. Like, bigger than a dorm refrigerator.
I’m always wondering what kind of constant noise might damage someone’s hearing (maybe develop tinnitus or long term hearing loss etc)? Is it only the volume or also duration and frequencies etc? Is there a risk having a noisy air purifier on all night?
Wonder no more. There is mountains of research on this for occupational health concerns. As long as your fan is <70dB there is virtually no risk to your hearing.
There might be some to your dog, on the other hand. Anecdotal, but my dog went deaf pretty early and he sleeps in a room where I run an air purifier all night. Not sure if there is correlation or causation there but that's my little anecdata.
This makes me wonder, for a truly travel-size solution (or just otherwise compact needs), if there's a viable alternative that directs filtered air at a sleeper's head? In other words, would the net effect be equivalent for one person (such that they're breathing more or less the same cleanness of air)?
I grasp that such an approach might draw unfiltered surrounding air along with the filtered stream of air, and imagine that it would likely be easily overwhelmed by a steady supply of exceptionally polluted air (wildfire smoke or simply a heavily polluted urban area), but I still would be interested in knowing if the compromise never overcomes a level of placebo effect, or if there's a point where it actually achieves measurable benefit (both in efficacy and portability—like a even more compact and directional version of the Corsi-Rosenthal computer fan solution.)
However, testing seems to show that the clean air flow is neither wide nor far; it would only be effective right next to your face and you can't really move:
My aunt is immunocompromised and carries one around with her in crowded situations, keeping it pointed right at her face 8-12in away. It works well for her, especially since she's had a lung transplant and doesn't do well with a mask.
I have seen models designed this way! Vornado used to make one, I think it's discontinued.
These directed-air "personal models" make a lot of sense to me... at least in theory. I haven't seen them properly tested.
The big air purifiers work great.. if the room is closed up. But their effectiveness approaches zero if you have the windows open or otherwise have unfiltered air entering the room. Which is kind of important, if you don't enjoy breathing in sky high levels of CO2. (If one's allergies are bad enough, or a wildfire is raging outside, CO2 might of course be preferable to particulates)
If you want the better sound but don't care about the purifier, then get a DOHM sound machine. It uses a fan and sound great, and I'd guess the energy consumption is pretty trivial.
this feels like a 'dose makes the poison' scenario. you're talking about maybe $10 of difference annually if both were run continuously. and that's only if you bought an inefficient air purifier - if you elected to use, for eg, four Arctic P14 PSTs in a CR box then that's maybe double the kWh. this ends up being a couple of bucks more annually for the added benefit of having better air quality
Ive been relying on an air purifier or desk fan as white noise for years but recently switched to airpods 5 anc which has pretty much replaced the former
I run a Midea dehumidifier around the clock during the summer. The inverter driven compressor noise is quite pleasant. It masks higher pitch tinnitus very well.
I have one in the bedroom. On low, I barely hear it during the day (extra ambient noise from outside) but at night the white-noise is subtle but effective. That said, I don't like "loud" white noise, just a quiet hum.
YSK on low you won't be getting much air cleaning power. All air purifiers are rated based on their top fan speed.
Housefresh, which is a criminally underrated review channel btw, recently did a comparison of PC fans for this purpose. The Thermalright TL-14C family came out strong in the "Silent" category, with the best ultra-quiet 24/7 fan speed performance. This comes at the cost of slightly worse max speed CADR vs the venerable Arctic P14.
IQAir HyperHEPA is substantially worse than the AirFanta 3Pro. The 3Pro gives you about 10x more clean air per dollar (2 CFM/$ vs 0.2 CFM/$), and 2.5x more clean air at a given noise level (45dBA: 213 vs 86 CFM).
I agree big fans moving slowly is better all else equal, and something AirFanta-like that used a 12" fan could be even better.
If you can tolerate the in-ear physical sensation, Etymotic makes some fantastic earplugs for reducing noise. I similarly found even small noises to be distracting, and I couldn’t avail myself of earplugs or noise cancelling headphones because they also felt distracting. The clever thing that Etymotic did is design to reduce noise evenly across the spectrum, so it feels like turning the world’s volume knob down, rather than unevenly suppressing certain frequencies. Noise seems qualitatively less distracting with “the volume turned down” in this way, and the uneven suppression turned out to be the part that bothered me about other options. I consider myself sound-sensitive yet these things made a 14-hour flight in the same row as a crying baby quite tolerable (to both mine and the suffering parents’ relief). Your mileage may of course vary but this was a big QoL upgrade for me and it may be for you too.
It's a good start, Etymotic makes some of the most uncomfortable earplugs (the most uncomfortable I've ever worn), they sound fine.. as long as you don't need to lie down or rest your head.
The naming isn't great in the competition, but: Alpine, EarGasm, EarPeace, Loops are significantly better. Recent Alpine reviews suggest a material change - so maybe not them (haven't tried the new ones). They all come in different editions which is mostly about which frequencies they block/allow through.. loop is trying to push the price boundary (probably avoid, especially their "active" line).
All better than basic fluorescent foam earplugs though, easier to use and better sound blocking (the good audio ones allow you to speak/hear voices at close to normal volume in front of a 90dB sound stage)
I've been doing this for literally decades. Now when I go to someone else's home without an air purifier it feels painfully quiet AND I can almost feel the stale air. I much prefer it even if it's just some minor placebo effect.
It just looks like fog, but it is smoke, and the sky has an unusual orange color. Smells and tastes like you are standing in the path of a campfire, but you can't move out of the way. It irritates your eyes and throat if you spend more than 20 mins out there. You can go inside, but if the building you are in is leaky, it will smell like smoke inside there too.
The actual fire was hundreds of miles away. You can try driving in any direction for hours and not be clear of the smoke. Still, compared to other areas, this is barely worth complaining about.
My allergies became generally better at all hours just from sleeping in super cleaned air.
Why? Reducing baseline inflammation perhapse? Maybe decreased inflammation during sleep helps too, improved breathing? idk. Whatever it is this organism seems to prefer it.
Even when exposed to allergens during the day the run up to sneezing is much slower or doesn't happen.
This made me lol. I’ve been using an air purifier solely for the purpose of generating white noise. I don’t recall when I started doing this, but it’s been many, many years. The functionality of the air purifier wasn’t even a thought in my mind.
An air purifier is the best noise machine for me, much better than the white noise machines with the tinny speakers. Even the brown noise setting on those isn't nearly deep enough to let me sleep.
Totally agree. I've never liked the speaker generators. The old school DOHM models are way better because they do not use a speaker, they have a fan inside.
The Comega air filter is nicer sounding (and at “high” louder) than Dohm IMHO
The bigger the fan the better, IMO. I really love those cheap square box fans... It's hard to beat that deep, low hum that small speakers and small fans just can't replicate.
Now that I think of it, back when I was a kid in the 90s, there was a circa-70s oscillating fan that my family kept in the living room during the summer, and the noise it made was quite pleasant. The oscillation added a gentle rhythmic quality that made it even nicer.
I’d never put two and two together until now, but that fan had to have been a major factor in some of the unexpectedly great naps in that room.
We had a circulating fan from the 50s that had very little in way of a cage with metal blades. The fan was heavy as you might imagine from the time period. It worked great. It was definitely something we were repeatedly warned about it as kids to not put fingers/hands in it. The house was a pier&beam with the AC vents in the floor. The fan sat on the floor next to one of the vents to blow towards the couch. I'd agree that it had influence on naps as well
There are 20" square box fans that have a built in slot for a 20x20x1 filter. It's advertised as having a slightly more powerful motor. It is a good noise machine while also getting the added benefit of filtered air instead of just noise
Any recommendations? I'm finding a Lasko that looks fine but is out of stock everywhere.
I just run a fan and point it towards the wall. I have never liked any of the speaker-based noise machines.
You can easily send white noise to good speakers, if you have any. There are free apps for it, not to mention hours-long YouTube videos with white/pink/brown noise.
Yea, having it and using it at max just as I go to bed just makes me feel much better for the air I'll be breathing while sleeping. I also used to always fall asleep to some noise or music, so this is such a nice replacement
What are people's target AQIs? I have indoor monitors in our high-rise building in SF and live 100 m from the freeway and we have:
That's the baseline. When we're cooking, like now, it's: None of those seem particularly concerning. We have a gas range, and 15 min past the end of cooking everything is fine. I must imagine that most people don't live right next to the freeway so they probably have even better air quality except during wildfire season.CO2 - I'm thrilled with anything less than 800 ppm (half justified by being the lowest number I've ever seen a study suggest might have health effects, half justified by being at a point where I personally don't notice that I'm more drowsy).
PM2.5 - My impression is the health risks here are more cumulative exposure (and include things I'd like to go without in my life, like alzheimers) and a pretty straight line of "lower is better all the way to zero". The WHO's guideline is mean exposure of 5 µg/m³ so I guess I'd adopt that if I had to put a number on it. (But it's a mean, I wouldn't worry about briefly exceeding it)
PM10 - No real opinion (I'd rather worry about PM2.5)
VOC index - I'm not sure this is a standardized thing, but the version I've come across is an index relative to the average that particular sensor has seen in the last 24 hours. So there's no standard possible here.
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As for a gas range I would worry about NOX considering the studies with them causing and aggravating asthma. That said your CO2 levels are low so I suspect you might have sufficient ventilation that this isn't a huge issue for you (especially if that ventilation is in the form of a fume hood over your stove that you actually use).
CO2 by itself doesn't appear to be a problem until some truly absurd levels are somehow achieved.
CO2 is usually a proxy for air quality because outside is usually something consistent like 400 therefore deviation from that figure indicates staleness.
Careful!
https://senecaeffect.substack.com/p/the-other-side-of-co2
Ahh yes, that old CO2 cognition scaremongering.
Let's just say, if you look closely at the meta-analyses, all the effect size goes away if you omit one certain author....
If true, SAT scores should systematically vary by hundreds of points depending on which room you take it in. This is not observed.
I don't have the list of relevant studies I've read on hand atm but there was at least one where they simply pumped in CO2 (or didn't) and had an effect showing pretty directly that CO2 itself is problematic at reasonably low levels - as well as potentially being an excellent proxy for other air quality issues. Problematic in a "makes you drowsy/stupid" type of way - not a "kills you" type of way. Though there's also at least one correlative studies suggesting it might have long term health effects (which really wouldn't be surprising if it has any short term effects).
Besides which, proxy or directly high CO2 means you should ventilate...
the military has conducted studies where submariners were exposed to a PPM of 1000s with no ill effect. I suppose they were trying to determine how hard they need to scrub.
having said that, it's possible they omitted what other gasses and %s they used for advantage. there could be some mitigation possible there.
Submarines: 3000ppm. Here is a study with 5000ppm CO2 and no decision-making impediment was found: https://pubmed.ncbi.nlm.nih.gov/29789085/
I have to say, I'm not convinced those studies are legit.
VOC index means literally nothing. (I've read the datasheet, implemented some kludges to log raw data, and contemplated the formulas. The data is high-pass filtered. You literally cannot conclude anything about a single measurement if you assume the sensor is somehow magically perfect. You might conclude that there is more VOC (or less -- not all VOCs have the same sign in their effect) when cooking than when not cooking.)
I target 0 PM2.5, but this only necessarily makes sense as a target if you have the ability to filter your home's supply air. And a good vent hood should be able to avoid any detectable bump while cooking (although a vent hood without filtered makeup air may cause a bump due to increased infiltration of exterior air).
What sensor, exactly, are you describing here? Different VOC sensors have different gas sensibilities, as well as different algorithms to interpret the gas sensor raw data.
High pass or low pass? Many instruments have a low pass filter. Very few have a high pass filter.
High pass. Probably actually band pass.
The instrument is pretty crappy - it has basically no calibration or, AIUI, long term stability. So you can’t really use it to characterize the chemical content of the air. What you can do is observe changes. I’m guessing the manufacturer wanted to avoid people getting confused by the absurd raw reasons, so they came up with a formula called “VOC Index” that HPFs the data. It will average 100 IIRC. You’re supposed to use it to notice events that cause changes - if it hits 170 every day at 2 PM them you can guess that something’s happening at 2 PM.
None of this is in the chip. It’s implemented by the driver. There’s an implementation in esphome, for example.
There's either a typo or something wrong with your sensor: you can't have pm10 < pm2.5.
(Equivalent to saying you have more people under 2.5 years old than under 10 years old.)
Transcription error there, you’re right, from Airgradient.
What? pm2.5 is smaller than pm10. You can have a bunch of larger particles that aren't small
pm10 is the mass concentration of particles with aerodynamic diameters up to approximately 10 µm, including PM2.5, so Jefftk's analogy was right. there must some kind of typo or measurement error
We have higher numbers than those and live fairly far from any freeway. Maybe your high-rise is doing better than you think.
Depending on the month, my kitchen AQI averages between 1-4, representing PM2.5 values of 0.1 - 0.8 ug/m^3. Bedrooms are likely better as they don't have the gas stove.
CO2 while occupied is generally under 750; I'd prefer to keep it under 700 but we also balance that with energy efficiency for that make-up air; I don't have an ERV, so we suffer a little there.
(We don't live by a freeway but - (a) Pittsburgh's air isn't great; and (b) the canadian wildfires were pretty bad here at times this summer, and that was what caused that 0.8 ug/m^3 pm2.5 spike).
We have, um, a lot of air filters left over from covid, though, so we're a little spoiled in terms of being able to manage AQI easily.
An air purifier is a good addition to a kids bedroom.
I got one during Santa Cruz wildfires in 2020 and now the kids have a pavlovian reflex to sleep once that gets turned on.
Ikea makes an air-purifier table, which is a end-run around it being a useless box in the room when switched off.
It's fairly expensive, not as good as a purpose built one, but it blends into the average room pretty well.
I have 4 Coway and 2 Winix purifiers and I can confirm: they're great sleep noise generators! The plastic front pieces and the filters themselves block/baffle any high frequency noise from the fans, leaving you with a pleasant low/mid frequency whooooooosh. I like it better than the sound from small cheap solid state machines; their small speakers can't do low frequencies.
Hmm. The word "most" is doing a lot of work here.Depends if you enjoy fresh air when you sleep or not. If you've ever monitored CO2 levels you know how quickly they climb in a closed room.
But, if you are blowing fresh air into a room, or have the windows open, the filtration effectiveness of these units approaches zero pretty rapidly. And these air purifiers aren't exactly free to run: they use ~50-100W of power and if you run them 24/7 you can expect to spend $100+ per year on filters.
So there's no perfect answer...
Most people would just leave the window open <1", which keep CO2 down yet air purifiers still work well.
> ~50-100W of power
That sounds too high? An AirFanta 3Pro on "2" is 141 CFM at under 5W https://www.jefftk.com/p/running-an-air-purifier-on-batterie...
That’s the design appeal of ionizers like BlueAir (not most ionizers, but specially those designed to supposedly prevent ozone production). They comparatively sip power while getting the same measured reduction in particulates and ozone.
There are also electrostatic air filters, but those tend to need an activated carbon stage to be actually good all things put together.
I've been using the air purifier as a white noise machine for 5 years and I couldn't be happier. Currently sitting in a room with PM2.5 at 1 µg/m³
I bought the Ikea (FÖRNUFTIG) because I was worried that lesser known brands on Amazon might go out of business, making it hard to find replacement filters later
My partner and I were just discussing whether our air purifier actually does something other than make noise, and whether the air quality indoors is better or worse than outdoors.
How do y'all track air quality in your home?
I bought some levoit core 300s purifier and after a minute it seemed to have made air so dry i started to have dry throat and light coughing. Thought I'd need a humidifier too .. but I just sold it back.
I've been quite happy with a recent AirGradient One purchase. It's easy to use and had decent reviews when I did some research.
I also like the fact they offer a discount if you buy it as a kit to be assembled (it's very easy to put together).
IKEA has a few air quality meters. Good accurate sensors are rather expensive however, for both particulates and CO2.
Yeah we do this at home. Bedrooms plus the great room on the kitchen side.
It might not be guaranteed to help, but it sure doesn't hurt since it's cleaning the air anyway.
They work great, better than a fan because it clears the air.
I have one blowing gently across my face while I sleep. It cools me down, and blocks out the highway noise.
Noise pollution is known to have adverse health effects, maybe its better to not cover one noise with another, even louder one? Or invest in sound insulation, damage compounds over decades.
Many people don't have the option to isolate their houses better.
But, if I'm not mistaken, the damage you speak of is caused by disrupting sleep. So the idea is that if a white noise generator can drown out the interruptions, it helps you sleep better. There are studies that say noise doesn't help, and there are those that say it does. And it's all real-life medical research, so pretty unreliable. I found one controlled study (https://doi.org/10.1093/sleep/zsag001), but it's small, and only 7 days, and it's in a lab, so not guaranteed to translate to normal conditions either.
And don't ignore the placebo effect. Perhaps believing that pink noise helps is sufficient for some.
Perhaps a better recommendation is good ear plugs.
My dog gets stressed out by fireworks, even if she wasn't sleeping. Being startled by a loud sound isn't fun, right?
I expect there are more complex stress response mechanisms at play here, not just disturbed sleep.
I bought a large soldering iron air purifier and it turns out to be great; it has a continuious speed selector, easy to replace filters, and very pleasant spectrum. I like it better than the air conditioner, which cycles on and off noisily.
One of the best air purifiers you can get (linked in the above writeup) uses PC fans and a custom controller where you can control the speed/volume: https://housefresh.com/best-air-purifiers-we-tested/#2-best-...
Why is this so expensive? It's literally 4 PC fans and some plastic trays? I presume you bring your own filters.
You can make your own to save money, I made this project for example. I paired it with an Air-1 sensor and home assistant to ramp up and down the downs in real time according to the live air quality readings.
https://makerworld.com/en/models/2470181-nukit-tempest-euro-...
Filters are included, as well as high quality fans, AC/DC converter and speed controller, and the portable/collapsible enclosure. It's really not that expensive vs trying to put together the parts yourself, and it's tested to work very well compared to other more expensive filters.
Those fans will not have sufficient static pressure to be useful. These makeshift purifiers may be great in a pinch (wildfire season and stores are all out), but far from the best.
This is indeed the "conventional wisdom," but if you do the math it turns out this is incorrect.
The trick is to use high-airflow MERV 13 filters (ideally 3M 1900, which has high pleat count and low resistance) instead of high-resistance HEPA filters, so axial PC fans can generate enough pressure.
You want at least MERV 15 so that virus sized particles get filtered in meaningful amounts, but yes the guy above you is wrong and choking on dirty air
At that point, you’re not doing any actual air filtering. Just use them as fans instead.
Merv-13 means it filters at least 75% of the particles passing through it.
For a standalone air filter which is pushing the filtered air into the same room its drawing from, we can assume reasonably good mixing of the intake and exhaust air. Thus to be equivalent to a HEPA-filter it only needs 1/3rd more airflow... Which really isn't much.
This doesn't follow for a a fancier setup where you're taking dirty air and blowing it into a cleanroom or something... but that's not how we're typically using household air filters.
Is it safe to assume all particles are equally as likely to be filtered, or are there particles that HEPA will filter that a MERV-13 will never filter no matter the number of cycles?
75% refers to the Most Penetrating Particle Size (MPPS), so they intentionally measure at the worst-case size so you don't have that problem. All other sizes are filtered at a higher percent.
Go look up MERV ratings there’s several in between HEPA and MERV-13. The stuff right below HEPA like MERV-15 gives best of both worlds.
The linked PC-fan purifier has been tested and shown to purify air faster than the conventional alternatives, and are not makeshift, so I'm not sure what you are referring to.
From the specs it looks like they are probably closer to higher-static-pressure server fans, the CADR is a few hundred CFM and it pulls 30+ watts. And as with many of these designs, you can compensate for low pressure performance by increasing filter surface area... the greater the surface area the lower the pressure drop. Of course, the problem with this is you are just spending more money on filters, which is the expensive part.
The filter cost for the AirFanta 3 doesn't seem particularly high? In fact it seems cheaper than competitors.
All the purifier companies realized they make more money selling overpriced filters, so $60+ for the OEM filters is common nowadays. Despite it just being a standard HEPA filter cut to a specific size.
Airfanta 3 Pro filters (four) - $57
Coway Mighty Filter - $60
Coway Mighty2 Filter - $70-$80
I'd be concerned about the availability of filters after a few years. Some of these companies have been changing their models and filter type every year to add some nebulous feature. Others just go out of business.
Yeah, the retail prices of filters is all over the place because of the popularity of razor/blade model of pricing. I'm not talking about that, I'm talking about the BOM itself -- this device is using 4x the filter media of comparable filters, which would typically have one filter that size.
HEPA media itself is a commodity and aftermarket filters (and the BOM cost to the OEM) tend to level out at whatever rate is minimally profitable per area of filter media.
The upfront cost of this device is high for what you get, because you're mostly buying filter media. The device itself is not much of a polished product. I'm sure it works fine but I wouldn't want one in my living room.
I have three in my living room, and while they're not fashion they blend in fine: https://photos.app.goo.gl/wvRc4hEYqQep4zgd9
I leave them on setting 2 (unless someone is sick or we're having a lot of people over), and we get ~425 CFM for about $40/y in power (~5W each).
For cost over time, twice the filters means twice the replacement interval, so the additional filter cost cancels out.
But since you bought mostly media, you didn't get a housing that hides the media, and you get to look at any collected dirt for that longer interval as well...
I'm sure it works but like any engineering decision it has pros and cons.
However, if you really don't want to look at it, you can always flip most DIY designs inside-out so the fans blow in and dust collects on the inside instead of the outside! This doesn't clean the room quite as efficiently, but if the appearance of dust is a major concern that should be a fix.
Yeah it’s functionally fine but I would opt to buy a more polished product for the above reasons. Probably would be great for a shop or similar, which is where I’ve done DIY purifiers myself. My personal favorite for cutting down on dust during home projects is a 20x20 furnace filter slapped on the intake side of a box fan. It requires zero extra parts or assembly.
Flipping the fans isn’t great because then you have to clean the fans, this is why draw-through is the standard configuration. Also many designs like this rely on negative pressure to seal properly or even stay together. You might just have the lid take off like a helicopter.
It just looks grey, but the housing is also grey, so I don't think it generally reads to people as dirty.
There's an Open Source tool for building your own that does all the calculations for you: https://filterboxbuilder.com
The Austin Air HealthMate is great as a noise machine. Very loud. It’s a HEPA filter and lasts 5 years. Never seen any other that lasts that long, but you pay for it upfront. after-market replacements are $250-300 for another 5 years.
They are truly excellent machines. I’ve used a couple of these over the years, never had an issue.
I have that machine. It seems better at filtering chemicals and VOCs but not great at filtering particulates. It gets rid of odors very well but my PM2.5 meter barely budges.
I have IQAir HyperHEPA filters, plus whole-house AprilAire HEPA filters on the HVAC equipment in the attic. I’m fine on particulates.
Where I need extra help is with VOCs in certain locations. Like, in or near bathrooms. Or the cat litter boxes. IQAir does sell their GC line for that, and we have a couple of those. But the activated carbon filter media is super expensive. And these things are huge. Like, bigger than a dorm refrigerator.
So, I welcome an alternative that does VOCs well.
Yeah, it's a completely different kind of air purifier than the "tape a HEPA filter to a fan" ones, which is why it costs $1,000 instead of $150.
Which PM2.5 meter do you have? I’ve been looking to buy one and AirThings keeps coming up.
I have a Temtop indoor air quality monitor. The exact model seems to have been discontinued but it can measure PM2.5 and formaldehyde.
I’m always wondering what kind of constant noise might damage someone’s hearing (maybe develop tinnitus or long term hearing loss etc)? Is it only the volume or also duration and frequencies etc? Is there a risk having a noisy air purifier on all night?
Wonder no more. There is mountains of research on this for occupational health concerns. As long as your fan is <70dB there is virtually no risk to your hearing.
There might be some to your dog, on the other hand. Anecdotal, but my dog went deaf pretty early and he sleeps in a room where I run an air purifier all night. Not sure if there is correlation or causation there but that's my little anecdata.
Health and safety regulations are all about noise levels and exposure duration, not frequencies
Alrighty, don't a lot of people already do this? Sometimes I'll do both an air purifier white noise and some music or something from myNoise
This makes me wonder, for a truly travel-size solution (or just otherwise compact needs), if there's a viable alternative that directs filtered air at a sleeper's head? In other words, would the net effect be equivalent for one person (such that they're breathing more or less the same cleanness of air)?
I grasp that such an approach might draw unfiltered surrounding air along with the filtered stream of air, and imagine that it would likely be easily overwhelmed by a steady supply of exceptionally polluted air (wildfire smoke or simply a heavily polluted urban area), but I still would be interested in knowing if the compromise never overcomes a level of placebo effect, or if there's a point where it actually achieves measurable benefit (both in efficacy and portability—like a even more compact and directional version of the Corsi-Rosenthal computer fan solution.)
There's an Airfanta 4Lite which uses laminar flow to achieve that:
https://air-fanta.com/products/airfanta-4lite
However, testing seems to show that the clean air flow is neither wide nor far; it would only be effective right next to your face and you can't really move:
https://www.reddit.com/r/Masks4All/comments/1di1n4t/can_a_po...
There aren't a lot of use cases for it.
My aunt is immunocompromised and carries one around with her in crowded situations, keeping it pointed right at her face 8-12in away. It works well for her, especially since she's had a lung transplant and doesn't do well with a mask.
I have seen models designed this way! Vornado used to make one, I think it's discontinued.
These directed-air "personal models" make a lot of sense to me... at least in theory. I haven't seen them properly tested.
The big air purifiers work great.. if the room is closed up. But their effectiveness approaches zero if you have the windows open or otherwise have unfiltered air entering the room. Which is kind of important, if you don't enjoy breathing in sky high levels of CO2. (If one's allergies are bad enough, or a wildfire is raging outside, CO2 might of course be preferable to particulates)
You can use them as random number generators, to replace your lava lamp for example.
I'll stick with RFC 1149.5.
Air purifier is gonna use a lot more energy than just a small speaker. The energy cost swamps everything long term
If you want the better sound but don't care about the purifier, then get a DOHM sound machine. It uses a fan and sound great, and I'd guess the energy consumption is pretty trivial.
this feels like a 'dose makes the poison' scenario. you're talking about maybe $10 of difference annually if both were run continuously. and that's only if you bought an inefficient air purifier - if you elected to use, for eg, four Arctic P14 PSTs in a CR box then that's maybe double the kWh. this ends up being a couple of bucks more annually for the added benefit of having better air quality
I think $10 is too low an estimate.
An AirFanta 3Pro on low (2) is 5W, which is $10 on average (but more like $15 in high $/kWh places like MA and CA).
Some people are paying north of 0.50€/kWh (after tax), so this amounts to 22€ annually.
The point stands. If you care about this, it's a personal choice whether that comfort is worth ~20€. I would wager many people say it is.
swamps everything except for the health benefits
Ive been relying on an air purifier or desk fan as white noise for years but recently switched to airpods 5 anc which has pretty much replaced the former
I run a Midea dehumidifier around the clock during the summer. The inverter driven compressor noise is quite pleasant. It masks higher pitch tinnitus very well.
Does that mean your air doesn't get filtered if you stop or decide to turn down the white noise?
I prefer having quiet air filters that I can run all day (based on air quality) instead of noisy ones I only use at night.
If you turn it off, sure.
I have one in the bedroom. On low, I barely hear it during the day (extra ambient noise from outside) but at night the white-noise is subtle but effective. That said, I don't like "loud" white noise, just a quiet hum.
YSK on low you won't be getting much air cleaning power. All air purifiers are rated based on their top fan speed.
Housefresh, which is a criminally underrated review channel btw, recently did a comparison of PC fans for this purpose. The Thermalright TL-14C family came out strong in the "Silent" category, with the best ultra-quiet 24/7 fan speed performance. This comes at the cost of slightly worse max speed CADR vs the venerable Arctic P14.
https://www.youtube.com/watch?v=Rlz37IdCcIE
For air filtering, you want big fans that move relatively slowly. At least, at lower settings.
I still haven’t seen anything else that can compare to IQAir HyperHEPA filters. They use these things in hospitals.
IQAir HyperHEPA is substantially worse than the AirFanta 3Pro. The 3Pro gives you about 10x more clean air per dollar (2 CFM/$ vs 0.2 CFM/$), and 2.5x more clean air at a given noise level (45dBA: 213 vs 86 CFM).
I agree big fans moving slowly is better all else equal, and something AirFanta-like that used a 12" fan could be even better.
All my air filters are sized to clean air while being quiet.
Turning them up to med/high would just cause too much airflow.
Many air purifiers are silent on lower settings and louder on higher settings. If I want noise I turn mine up. If I want less noise I turn it down.
I use my philips as noise machine :P But like year ago it changed noise and I don't like it that much anymore
True, mine does that job really well too. Not too much high in it either, just a nice low rumble.
For sleeping I prefer rain sounds though
For me, that's another reason not to have one.
I like silence.
I consider noise from things like a refrigerator, or a computer case fan, to be distracting, and a reduction in the quality of my environment.
White noise is still noise, and there's no noise like no noise...
If you can tolerate the in-ear physical sensation, Etymotic makes some fantastic earplugs for reducing noise. I similarly found even small noises to be distracting, and I couldn’t avail myself of earplugs or noise cancelling headphones because they also felt distracting. The clever thing that Etymotic did is design to reduce noise evenly across the spectrum, so it feels like turning the world’s volume knob down, rather than unevenly suppressing certain frequencies. Noise seems qualitatively less distracting with “the volume turned down” in this way, and the uneven suppression turned out to be the part that bothered me about other options. I consider myself sound-sensitive yet these things made a 14-hour flight in the same row as a crying baby quite tolerable (to both mine and the suffering parents’ relief). Your mileage may of course vary but this was a big QoL upgrade for me and it may be for you too.
It's a good start, Etymotic makes some of the most uncomfortable earplugs (the most uncomfortable I've ever worn), they sound fine.. as long as you don't need to lie down or rest your head.
The naming isn't great in the competition, but: Alpine, EarGasm, EarPeace, Loops are significantly better. Recent Alpine reviews suggest a material change - so maybe not them (haven't tried the new ones). They all come in different editions which is mostly about which frequencies they block/allow through.. loop is trying to push the price boundary (probably avoid, especially their "active" line).
All better than basic fluorescent foam earplugs though, easier to use and better sound blocking (the good audio ones allow you to speak/hear voices at close to normal volume in front of a 90dB sound stage)
I’ll have to check these out! Thank you!
Agreed. I'd love to have air purification (and air circulation to reduce CO2) without noise, to the extent possible.
I prefer pink noise.
Agreed, possibly because it's spectrum distribution is a lot closer to natural sounds, like flowing water.
I've been doing this for literally decades. Now when I go to someone else's home without an air purifier it feels painfully quiet AND I can almost feel the stale air. I much prefer it even if it's just some minor placebo effect.
Glad to see I'm not the only person who does this
I've considered an air purifier for allergy reasons, but...
>removes smoke and infectious particles
Where do people live that they need to remove such things, 18th century London?
This is approximately what it looked like near my area in mid July for a few days.
https://commons.wikimedia.org/wiki/File:Wildfire_smoke_Wyand...
It just looks like fog, but it is smoke, and the sky has an unusual orange color. Smells and tastes like you are standing in the path of a campfire, but you can't move out of the way. It irritates your eyes and throat if you spend more than 20 mins out there. You can go inside, but if the building you are in is leaky, it will smell like smoke inside there too.
The actual fire was hundreds of miles away. You can try driving in any direction for hours and not be clear of the smoke. Still, compared to other areas, this is barely worth complaining about.
Anywhere in the US west of Texas and most of Canada.
I don't think the east coast escapes, they got slammed this year by Canadian wildfire smoke IIRC.
Infectious particles? In most of USA and Canada? I don't believe you.
I'm talking about smoke, I don't even know what an "infectious particle" is.
Me neither, and that's why I asked, but it apparently offended the HN commentariat.
Yes, there are viruses in USA & Canada.
Allergens are likely considered "infectious particles" for that particular sentence.
>Where do people live that they need to remove such things
SF Bay Area during the summer fires of a few years ago
I use mine just to purify air for my precious LTO tape drive. My baby doesnt like dust
Almost anywhere now in North America or Europe during the summer.
Doesn't even need to be during the summer.
Wind blows smoke around. There are currently fires in northern Michigan that are affecting the air quality in Chicago, which is 350+ miles away.
https://data.usatoday.com/fires/
Most of the world, unfortunately. Just look at an air quality map.
I live in an area where many of my neighbours can afford log burners and who don't care about the pollution
As an allergy enjoyer there is no air too pure.
My allergies became generally better at all hours just from sleeping in super cleaned air.
Why? Reducing baseline inflammation perhapse? Maybe decreased inflammation during sleep helps too, improved breathing? idk. Whatever it is this organism seems to prefer it.
Even when exposed to allergens during the day the run up to sneezing is much slower or doesn't happen.